Detection of Pb II in the Ultraviolet Spectra of Three Metal-poor Stars,The Astrophysical Journal Letters

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Detection of Pb II in the Ultraviolet Spectra of Three Metal-poor Stars
The Astrophysical Journal Letters ( IF 8.8 ) Pub Date : 2020-10-11 , DOI: 10.3847/2041-8213/abbc21
Ian U. Roederer _{1,

2} , James E. Lawler ₃ , Erika M. Holmbeck _{2,

4} , Timothy C. Beers _{2,

5} , Rana Ezzeddine _{2,

6} , Anna Frebel _{2,

7} , Terese T. Hansen _{8,

9} , Inese I. Ivans ₁₀ , Amanda I. Karakas _{11,

12} , Vinicius M. Placco _{2,

13} , Charli M. Sakari ₁₄

Affiliation

Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109, USA
Joint Institute for Nuclear Astrophysics—Center for the Evolution of the Elements (JINA-CEE), USA
Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623, USA
Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA
Department of Astronomy, University of Florida, Bryant Space Science Center, Gainesville, FL 32611, USA
Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA
Department of Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA
Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112, USA
School of Physics and Astronomy, Monash University, VIC 3800, Australia
ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
NSF’s Optical-Infrared Astronomy Research Laboratory, Tucson, AZ 85719, USA
Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94132, USA

We report the first detection of the Pb ii line at 2203.534 Å in three metal-poor stars, using ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We perform a standard abundance analysis assuming local thermodynamic equilibrium (LTE) to derive lead (Pb, Z = 82) abundances. The Pb ii line yields a higher abundance than Pb i lines by +0.36 ± 0.34 dex and +0.49 ± 0.28 dex in the stars HD 94028 and HD 196944, where Pb i lines had been detected previously. The Pb ii line is likely formed in LTE, and these offsets affirm previous calculations showing that Pb i lines commonly used as abundance indicators underestimate the Pb abundance in LTE. Pb is enhanced in the s -process-enriched stars HD 94028 ([Pb/Fe] = +0.95 ± 0.14) and HD 196944 ([Pb/Fe] = +2.28 ± 0.23), and...

中文翻译：

三颗贫金属星在紫外光谱中的Pb II检测

我们报告了使用哈勃太空望远镜上的太空望远镜成像光谱仪获得的紫外光谱，在三颗贫金属星中首次检测到2203.534Å的Pb ii线。我们执行标准的丰度分析，假设局部热力学平衡（LTE）得出铅（Pb，Z = 82）丰度。在HD 94028和HD 196944恒星中，Pb ii品系的丰度比Pb i品系高+0.36±0.34 dex和+0.49±0.28 dex，其中先前已检测到Pb i品系。Pb ii线很可能在LTE中形成，这些偏移量证实了先前的计算结果，该计算结果显示通常用作丰度指标的Pb i线低估了LTE中的Pb丰度。富含s过程的恒星HD 94028（[Pb / Fe] = +0.95±0.14）和HD 196944（[Pb / Fe] = +2.28±0.23）中的Pb增强，并且...

更新日期：2020-10-12

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